This invention relates generally to Ethernet repeaters, and more particularly to transfer of data packets from a first Ethernet collision domain to a second Ethernet collision domain.
Computer networks utilizing Ethernet protocol as described in Standards such as: ANSI/IEEE 802.3, xe2x80x9cCarrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specificationsxe2x80x9d, 1988, 1989; IEEE 802.3b, c, d, and e, 1989 Edition, xe2x80x9cSupplements to Carrier Sense Multiple Access with Collision Detectionxe2x80x9d,; ISO/IEC 8802-3, ANSI/IEEE Std 802.3, CSMA/CD xe2x80x9cCarrier Sense Multiple Access with Collision Detection Access Method and Physical Layer Specificationsxe2x80x9d; IEEE Std 802.3u-1995, xe2x80x9cMedia Access Control (MAC) Parameters, Physical Layer, Medium Attachment Units, and Repeater for 100 Mb/s Operation, Type 100BASE-Txe2x80x9d, Clauses 21-30; and IEEE Standard 902.9, Local and Metropolitan Area Networks, IEEE Standard Specification of ISLAN15-T, are common today.
A computer network implementing the Carrier Sense Multiple Access Method with Collision Detection (CSMA/CD) method of operation utilizes collision domains. In a collision domain, the stations attached to the network will detect a collision in the event that two or more stations attempt to transmit on the network at the same time. A collision domain is limited in its spatial extent by technical factors, principally the speed at which a station can respond to detection of a collision, the speed of transmission on the attachment medium, the length of time of a minimum length message, etc.
A longstanding problem in design of computer networks is how to provide for forwarding of data packets from a first collision domain to a second collision domain. Repeaters, as described in Chapter 9 of the ANSI/IEEE Std. 802.3b, c, d, and e 1989 Edition mentioned hereinabove have been used to extend an Ethernet collision domain. Bridges, which are devices with a store and forward functionality and operative on data packets carrying the destination address of the desired destination end station, have also been used in the past to forward a data packet from a first Ethernet collision domain to a second Ethernet collision domain. Routers, also a store and forward device and operative on data packets addressed to the router, have been used to forward data packets from a first Ethernet collision domain to a second Ethernet collision domain.
Still unresolved is how to forward a data packet from a first Ethernet collision domain to a second Ethernet collision domain by a simple and cheap method
A repeater device for forwarding a data packet from a first Ethernet collision domain to a second Ethernet collision domain has a plurality of ports, each port for connection to an independent Ethernet collision domain, each port has an associated receive buffer and an associated transmit buffer, and there is a means for forwarding a data packet from the receive buffer of a receiving port to the transmit buffer of a transmitting port. A data packet received at the receiving port is then first stored in that port""s the receive buffer, is forwarded to the transmit buffer of the transmitting port, and is then transmitted from the transmit buffer by the transmitting port.
Further, the invention is an Ethernet repeater, having: a receive buffer to hold data received from a first Ethernet collision domain; a transmit buffer to hold data for transmission onto a second Ethernet collision domain; at least one internal bus for broadcast of received data from the receive buffer from the first Ethernet collision domain to the transmit buffer to prepare the received data for transmission onto the second Ethernet collision domain; to enable the transmit buffer, the receive buffer, and the internal bus serve to permit the first Ethernet collision domain and the second Ethernet collision domain to operate as independent Ethernet collision domains.
The repeater also has a switch having a first switch port and a second switch port; a first internal bus connected to the first switch port, and the first internal bus connected to the receive buffer; a second internal bus connected to the second switch port, the second internal bus connected to the transmit buffer, means for the receive buffer to broadcast onto the first internal bus data received from the first Ethernet collision domain; means for the switch to direct data broadcast onto the first internal bus by the receive buffer to the second internal bus; means for the transmit buffer to receive data broadcast onto the second internal bus, and for the transmit buffer to transmit the data onto the second Ethernet collision domain.
Also, the repeater has the first Ethernet collision domain operating at a first data rate, and the second Ethernet collision domain operating at a second data rate, and the first data rate is different from the second data rate. Further, the repeater has the at least one internal bus operating at a clock rate which is independent of a data rate of the first Ethernet collision domain and is independent of a data rate of the second Ethernet collision domain.
A repeater has a means for receiving packets from a source workstation on a first Ethernet collision domain and for transmitting the packets to a destination workstation on a second Ethernet collision domain; a buffer in the repeater for providing temporary storage of a packet received on the first Ethernet collision domain; means, responsive to the buffer being full, for the repeater to generate a collision in the event that a second packet is detected on the first Ethernet collision domain. Further, the repeater has a means for generating the collision by placing a back pressure packet in a transmit buffer of the repeater. In addition, the repeater has means for generating the collision by placing a data packet designated to be transmitted onto the first Ethernet collision domain into a transmit buffer of the repeater.